[PATCH RFC v2 4/5] dma: mpc512x: register for device tree channel lookup

[Alexander Popov]

From: Gerhard Sittig <gsi at denx.de>

register the controller for device tree based lookup of DMA channels
(non-fatal for backwards compatibility with older device trees), provide
the '#dma-cells' property in the shared mpc5121.dtsi file, and introduce
a bindings document for the MPC512x DMA controller

Signed-off-by: Gerhard Sittig <gsi at denx.de>
---
 .../devicetree/bindings/dma/
mpc512x-dma.txt        |   55 ++++++++++++++++++++
 arch/powerpc/boot/dts/mpc5121.dtsi                 |    1 +
 drivers/dma/mpc512x_dma.c                          |   21 ++++++--
 3 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/dma/mpc512x-dma.txt

diff --git a/Documentation/devicetree/bindings/dma/mpc512x-dma.txt
b/Documentation/devicetree/bindings/dma/mpc512x-dma.txt
new file mode 100644
index 0000000..a4867d5
--- /dev/null
+++ b/Documentation/devicetree/bindings/dma/mpc512x-dma.txt
@@ -0,0 +1,55 @@
+* Freescale MPC512x DMA Controller
+
+The DMA controller in the Freescale MPC512x SoC can move blocks of
+memory contents between memory and peripherals or memory to memory.
+
+Refer to the "Generic DMA Controller and DMA request bindings" description
+in the dma.txt file for a more detailled discussion of the binding.  The
+MPC512x DMA engine binding follows the common scheme, but doesn't provide
+support for the optional channels and requests counters (those values are
+derived from the detected hardware features) and has a fixed client
+specifier length of 1 integer cell (the value is the DMA channel, since
+the DMA controller uses a fixed assignment of request lines per channel).
+
+
+DMA controller node properties:
+
+Required properties:
+- compatible:          should be "fsl,mpc5121-dma"
+- reg:                 address and size of the DMA controller's register set
+- interrupts:          interrupt spec for the DMA controller
+
+Optional properties:
+- #dma-cells:          must be <1>, describes the number of integer cells
+                       needed to specify the 'dmas' property in client nodes,
+                       strongly recommended since common client helper code
+                       uses this property
+
+Example:
+
+       dma0: dma at 14000 {
+               compatible = "fsl,mpc5121-dma";
+               reg = <0x14000 0x1800>;
+               interrupts = <65 0x8>;
+               #dma-cells = <1>;
+       };
+
+
+Client node properties:
+
+Required properties:
+- dmas:                        list of DMA specifiers, consisting
each of a handle
+                       for the DMA controller and integer cells to specify
+                       the channel used within the DMA controller
+- dma-names:           list of identifier strings for the DMA specifiers,
+                       client device driver code uses these strings to
+                       have DMA channels looked up at the controller
+
+Example:
+
+       sdhc at 1500 {
+               compatible = "fsl,mpc5121-sdhc";
+               /* ... */
+               dmas = <&dma0 30>;
+               dma-names = "rx-tx";
+       };
diff --git a/arch/powerpc/boot/dts/mpc5121.dtsi
b/arch/powerpc/boot/dts/mpc5121.dtsi
index 384e692..dae99b7 100644
--- a/arch/powerpc/boot/dts/mpc5121.dtsi
+++ b/arch/powerpc/boot/dts/mpc5121.dtsi
@@ -394,6 +394,7 @@
                        compatible = "fsl,mpc5121-dma";
                        reg = <0x14000 0x1800>;
                        interrupts = <65 0x8>;
+                       #dma-cells = <1>;
                };
        };

diff --git a/drivers/dma/mpc512x_dma.c b/drivers/dma/mpc512x_dma.c
index 8f6d545..3d79e3a 100644
--- a/drivers/dma/mpc512x_dma.c
+++ b/drivers/dma/mpc512x_dma.c
@@ -38,6 +38,7 @@
 #include <linux/io.h>
 #include <linux/slab.h>
 #include <linux/of_device.h>
+#include <linux/of_dma.h>
 #include <linux/of_platform.h>

 #include <linux/random.h>
@@ -939,11 +940,23 @@ static int mpc_dma_probe(struct platform_device *op)
        /* Register DMA engine */
        dev_set_drvdata(dev, mdma);
        retval = dma_async_device_register(dma);
-       if (retval) {
-               devm_free_irq(dev, mdma->irq, mdma);
-               irq_dispose_mapping(mdma->irq);
+       if (retval)
+               goto out_irq;
+
+       /* register with OF helpers for DMA lookups (nonfatal) */
+       if (dev->of_node) {
+               retval = of_dma_controller_register(dev->of_node,
+                                                   of_dma_xlate_by_chan_id,
+                                                   mdma);
+               if (retval)
+                       dev_warn(dev, "could not register for OF lookup\n");
        }

+       return 0;
+
+out_irq:
+       devm_free_irq(dev, mdma->irq, mdma);
+       irq_dispose_mapping(mdma->irq);
        return retval;
 }

@@ -952,6 +965,8 @@ static int mpc_dma_remove(struct platform_device *op)
        struct device *dev = &op->dev;
        struct mpc_dma *mdma = dev_get_drvdata(dev);

+       if (dev->of_node)
+               of_dma_controller_free(dev->of_node);
        dma_async_device_unregister(&mdma->dma);
        devm_free_irq(dev, mdma->irq, mdma);
        irq_dispose_mapping(mdma->irq);

--
1.7.10.4